In most types of electric products implemented through electric power transformers play an important role in power transformation or signal isolation. A general transformer has various electric parameters when in use that are preset at the stage of research and production, such as power conversion ratio, mutual inductance value generated when winding coils are energized or loss occurring when the current passes through the winding coils. Then design is made for the transformer structure such as winding coil, winding rack or iron core according to the aforesaid electric parameters. By adjusting the coil ratio of the winding coils or interval between the winding zones on the winding rack, the produced transformer can generate the electric parameters the same as the original design.
A conventional transformer includes a first winding wound by a primary coil, a second winding wound by a secondary coil and an iron core running through the first and second windings. The primary coil and secondary coil are respectively a low voltage coil and a high voltage coil. The high voltage coil generates a creeping discharge problem upon receiving an input voltage. If this creeping discharge is not being isolated, the lower voltage coil could be broken down by the high voltage to result in damage of the transformer. To remedy this problem, Taiwan patent Nos. 385047, 415625 and 420363 disclose a structure with an increased creeping distance to prevent the high-voltage breakdown phenomenon. But it still has a problem of being unable to wind the primary coil and secondary coil at the same time.
Moreover, the winding rack can be implemented in many types, mainly can be divided in a vertical type and a horizontal type. An example of the vertical type can be found in Taiwan patent No. M425378, while the horizontal type is found in Taiwan patent No. I371763. Either of them relies on machining or injection molding to form a fixed structure after the structural specification of the winding rack is determined. The so-called structural specification means the interval between the winding zones of various winding coils on the winding rack or the position of the iron core. Once the specification is determined, the winding rack cannot be altered or adjusted according to requirements. As a result, the winding rack has to be redesigned to comply with the requirements. In the event that the alteration of the specification is merely slight, the redesign of the winding rack increases the production cost. In addition, in terms of the electric parameters of the transformer, there is a great relationship between the winding rack structure and leakage inductance of the winding coils. To provide a transformer winding rack structure with adjustable leakage inductance between various winding coils is a commendable approach to overcome the aforesaid problems.